Determination of Palladium with
Beta-Furfuraldoxime J. R. HAYES AND G . C. CHANDLEE School of Chemistry and Physics, The Pennsylvania State College, State College, Penna.
T
H E Group VI11 metals are known to form inner-complex and penetration compounds readily and hence it is not surprising to find a considerable number of organic reagents proposed for the quantitative and qualitative analysis of some of these metals. The familiar reaction of dimethylglyoxime with nickel and palladium salts was apparently the first application of this type of compound to inorganic analysis (11). Since that time various dioximes, as well as other types of organic compounds, have been proposed as reagents for the detection and determination of palladium. As representative of these may be mentioned benzoylmethylglyoxime (S), a-nitroso-P-naphthol (8), salicylaldoxime (6), p-dimethylaminobenzalrhodanine (g), and p-nitrosodiphenylamine (12). It has been convincingly demonstrated (1) that the formation of the chelate compounds with dioximes is due t o the The compound presence of the system -N=C-C-N--. used in this work, beta-furfuraldoxime, does not possess this atomic grouping, but was found to precipitate palladium completely. Therefore it is natural to find a different type of compound formed, one which is evidently an addition rather than an inner-complex compound. Beta-furfuraldoxime was found to be well adapted to the gravimetric determination of palladium, as well as to the separation of this metal from most others.
Materials Used The palladous chloride solutions were prepared by dissolving a known weight of the pure salt in a deiinite volume of 0.1 N hydrochloric acid, and were then standardized both by precipitation with dimethylglyoxime (IO) and by reduction to the metal with formic acid (IO). The palladous nitrate solution was prepared from the pure metal by solution in aqua regia and subsequent repeated evaporation with nitric acid until no test for chloride ion could be obtained. Standardization was by the same procedure as with the palladous chloride solutions. The palladous sulfate solution was also prepared from the metal by dissolving in hot concentrated sulfuric acid, followed by appropriate dilution and standardization by the procedures indicated above. The beta-furfuraldoxime was obtained from the Eastman Kodak Company and used without further purification. I t had a melting point of 88-90' C. A solution of the reagent was prepared shortly before use by dissolving 10 grams of the oxime in 100 ml. of alcohol. The solutions of inorganic ions were made up from salts of reagent grade. In most cases the concentrations were adjusted so as t o give closely 1mg. per ml. of the ion in question. All other reagents used were of c. P. grade.
Zr, Sn++, Sn++++, Ce+++, Pb, Th, PO4---,
VOa-, As+++,
As+++++, Sb, Bi, GO,--, W04--, Mood--, Cr+++, Mn++, Mn04-, Fe+++, Co, Ni, Ru+++, Rh+++, Os++++, Ir++++, and Pt++'+. Ceric solutions were found to give a yellow precipitate which, however, was far from quantitative. Auric ion gave, on standing, a brown precipitate which is probably chiefly metallic gold. Ferrous ion gave a red color with the reagent in both neutral and acid solution. Palladous ion yielded a heavy yellow precipitate from acid solution, and this precipitate was found to be quantitative for palladium.
Procedure for Determination of Palladium The palladous chloride solution, containing about 0.03 gram of palladium, is diluted t o about 100 ml. and the acidity is adjusted t o approximately 3 per cent hydrochloric acid (specific gravity 1.19, 38 per cent hydrochloric acid by weight) by volume. Close control of the acidity is not essential, as good results were obtained in solutions containing more than 10 per cent hydrochloric acid by volume. The palladium is then precipitated by the addition of 2 ml. of the alcoholic solution of the oxime. The curdy, light yellow precipitate which forms immediately is stirred briefly and allowed t o settle for an hour or longer. Precipitation is evidently complete in a very short time, as variations in the time of settling ranging from a few minutes to several days caused no noticeable difference in the results. The precipitate is next filtered on a weighed Gooch filter and washed with about 50 ml. of cold 1 per cent hydrochloric acid, followed by the same volume of water. Considerably larger volumes of the wash liquids may be used without affecting the results. After washing, the precipitate is dried for 2 hours at 110" C. and weighed. The time of drying may be safely extended without fear of decomposition of the precipitate but the temperature must not be allowed to rise much above 110' C. The theoretical factor for palladium, corresponding to the formula Pd(CaH30CHNOH)&, is 0.2669 and this value is used in calculating the results. Further evidence in support of this formula is given below. Table I gives the results of a few determinations in solutions containing palladium alone. TABLEI. DETERMINATION OF PALLADIUM
Qualitative Tests The action of beta-furfuraldoxime was h s t studied qualitatively with various ions. The procedure followed in most cases was to add 1 ml. of the alcoholic solution of the oxime to 5 ml. of the solution to be tested. As far as solubility relations allowed each ion was tested with the reagent in neutral, slightly acid, and slightly ammoniacal solution. The "neutral" solutions were those obtained by dissolving the pure salt in water, disregarding changes in acidity due to hydrolysis. With some of the less common ions the amounts used were smaller and the reactions were observed on a spot plate. The following ions were tested and gave negative results: Li, Na, K, Rb, Cs, Cu++, Ag, Be, Mg, Ca, Sr, Ba, Zn, Cd, Hg+, Hg++, Al,Tl+, BOI-, Sc, La, Tb, Er, Sm, Nd, Pr, Yt, Ti++++,
Palladium Present (as PdCh) Gram
Palladium Found Gram
0.0018 0.0018 0.001s 0.0179 0.0179 0.0179 0.0186 0.0186 0.0186 0.0186
0,0019 0,0018 0.0018 0.0177 0.0178 0.0177 0.0186 0.0186 0.0187 0.0186
Difference
Mo .
0.1 0.0 0.0 -0.2 -0.1 -0.2 0.0 0.0
0.1 0.0
Palladium Present (as PdClz) Gram 0.0227 0.0227 0.0227 0.0227 0.0300 0.0300 0.0300 0.0300 0.0300 0.0300
Palladium Found Difference Gram Mg I
0.0229 0.0227 0.022s 0.0228 0.0300 0.0299 0.0300 0.0301 0.0299 0.0299
0.2 0.0 0.1 0.1 0.0 -0.1 0.0 0.1 -0.1 -0.1
Composition of Precipitate Several grams of the precipitate were prepared, carefully washed, and dried to constant weight. Qualitative analysis indicated the presence of chlorine, nitrogen, and palladium. The quantitative analysis for chlorine was carried out by t h e Stepanov method (Q),for nitrogen by the Kjeldahl procedure (4),and for carbon and hydrogen by both the semimicrotechnique of ter Meulen and Hesslinga (6) and the conventional macrocombustion with the apparatus slightly modified, as 49 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
492
described by Renoll, Midgley, and H e m e (7). The palladium content was determined by the gravimetric method with dimethylglyoxime (IO). The following results were obtained: Carbon Hydrogen Xitrogen Chlorine Palladium
29.85, 2.51, 6.97, 17.89, 26.68,
Found
Average
%
%
%
30.27 2.56 6.98 17.71 26.71
30.04 2.52 7.00 17.73 26.69
29.97, 30.99 2.63, 2.55 6.95, 7.01 17.48, 17.77 26.74, 26.70
Calculated
The average values indicate the formula Pd(C4H30CHNOH)2C12, which is a coordination compound similar to that formed with pnitrosodiphenylamine and palladous chloride (12). TABLE 11. SEPARATION OF PALLADIUM FROM PL.4TINUIv1, RHODIUM, RUTHENIUM, AND IRIDIUM Palladium Present (as PdCld Gram 0.0018 0,0018
Metals Added Gram 0.02 each of P t + + + + , R u + + + , R h + + + .and I r + + + +
Palladium Found Difference Gram Mg. 0.0019 0.1 0.0018 0.0
Vol. 14, No. 6
TABLE11'. SEPARATION O F PALLADIUM FROM ASIONS Palladium Present (as PdClz) Gram 0.0186 0.0186 0.0186 0.0186 0.0300 0.0300 0.0300
Negative Ions Added Gram 1 . 0 of Pod---, 0 . 2 each of -kSo4---. and 0 . 1 each of MoO4-- and WOI--
vas-.
0 . 2 each of BOs--- and &Os--
Palladium Found Difference Gram Mg. 0,0185 -0.1 0.0186 0.0 0.0186 0.0 0.0186 0.0 0,0300 0.0 0.0300 0.0 0.0300 0.0
ible, as Table IV shows. The procedure was the same as for a pure palladium sample and the results were again calculated by means of the factor 0.2669. INTERFERING IONS.Gold was found to be partially reduced to the metal by the reagent and the direct separation of gold and palladium by this method is not possible. Ceric ions yield a precipitate with the oxime and hence also interfere. Those ions which form insoluble chlorides are also precipitated and hence must be removed before the determination of palladium is attempted. O F PALL.4DIWM IN PRESEXCE TABLEv. DETERMIXATIOK YITRATE AND SULFATE
0.06 of P t + + + + 0 08 of R u t + + 0.02 each of R h G T + a n dI r + + ;
0.0300 0.0300 0.0300
0,0299 0.0301 0.0300
-0.1 0.1 0.0
Palladium Present Gram
XaNOy Added Grams
Nags04 Added Grams
Palladium Found Gram
OF
Differenae .Mq. " . I
Determination of Palladium PRESENCE OF OTHERCATIONS. To test the effi-
I N THE ciency of the method for separating and determining palladium in the presence of other metallic ions, synthetic samples were prepared and the palladium was determined by the regular procedure. Table I1 gives results for the determination of palladium in the presence of other platinum group metals. All were present as the chlorides and of the valences indicated. The theoretical factor 0.2669 was used in calculating the palladium content. In addition to the other platinum metals, separations from many of the more common metallic ions are readily possible. Various salts were added to the palladous chloride solutions to give the concentrations of metallic ions indicated in Table 111. Where antimony was present the acid concentration was about 7 per cent by volume and approximately 1 gram of tartaric acid was added to keep the antimony in solution. With this exception the regular procedure was used without modification and the results were calculated using the theoretical factor 0.2669. IN THE PRESENCE OF ANIONS. Determinations of palladium in the presence of various anions are also readily feasTABLE111. SEPARATION O F PALLADIUM FROM MET.4LS Palladium Present (as PdC12) Gram 0.0227 0.0227 0.0227 0.0300 0.0300 0.0300 0.0300 0.0300 0.0186 0.0186 0.0300 0.0300 0.0186 0.0186 0.0300 0.0300
Palladium Found Difference Gram Mg. 0.0227 0.0 0.0227 -0.1 0.0227 0.0 0 . 1 each of C u t T , Cd'+, B i T + T , 0.0298 -0.2 H g C T ,Sn+'-', S b * + - , Z n 7 + , 0.0300 0.0 and A1 0.0300 0.0 0.0300 0.0 0.0299 -0.1 0 . 1 each of T h + + T * + + - T 0.0186 0.0 Z r + - - + . .\In++. and'C:i-' 0.0187 0.1 0.0300 0.0 0.0301 0.1 0 . 1 each of Ca. J r , Ba, X g , Na, 0,0187 0.1 andK 0.0186 0.0 0.0300 0.0 0.0299 -0.1 Metals Added Gram 0 . 1 each of F e T t T , C o f T , C u * - , Xi*+, .\In-+, and H g + +
+
--
0.1 0.03004 2 2 0.0300 0.0 0.03004 2 2 0.0300 0.0 0.03O04 10 0 0.0299 -0.1 0.03O04 10 0 0.0299 -0.1 0,03000 0.0301 0.1 0 10 0 10 0.03004 0.0300 0.0 5 5 0.03004 0.0301 0.1 0.0300 5 5 0.0300" 0.0 0.0122 1 0.0122b 0 0.0 0.0122 1 0 0.0122b 0.0 0.0122b 0.0121 1 0 -0.1 0.0139 0.0 0.01390 1 0 0.01390 1 0 0.0140 0.1 0.01390 1 0 0.0139 0.0 4 Palladium present as palladous chloride. b Solution of palladous sulfate taken, precipitated and let stand for 2 hours in absence of chloride. Then 1 gram of sodium chloride added and determination completed and calculated according t o re ular procedure. 0 Solution of palladous njtrate taken, precipitate3 and allowed to stand for 2 hours in absence of chloride. Completed as in b.
PRECIPITATION OF A COMPLEX PALLADOUS SULFATE AND NITRATE. When the formula of the palladous chloride-betafurfuraldoxime precipitate had been established, it became of interest to ascertain whether analogous compounds were formed from palladous sulfate and palladous nitrate with the reagent. It was found that a precipitate could be readily obtained in each case, and several grams of each were prepared by direct precipitation of the palladous sulfate and palladous nitrate solutions. Bfter washing and drying to constant weight, these precipitates were subjected to analysis, with the results indicated below. The same procedures of analysis were used as with the chloride precipitate, although more difficulty was encountered in the combustion. Analysis of Palladous Sulfate Complex. Found: C, 37.34; H, 2.37; N, 8.85; Pd, 16.12; SO, 14.80. Calculated for CZOHzoN4OsPdSO4: C, 37.12; H, 3.12; N, 8.65; Pd, 16.50; sod, 14.84. This corn oaition corresponds reasonably well t o the formula Pd(C4H38CHN0H),SO4,whjch is different from the compound formed with palladous chloride. Analysis of Palladous i W r a t e Complex. Found: C, 41.81; H, 3.30; N , 10.42; Pd, 19.47. Calculated for CzoHlsN4OsPd: C, 43.75; H, 3.30; 1;) 10.20; Pd, 19.44. This composition agrees fairly well with the formula Pd(C4H3OCHSOH)z(C,Hr OCHKO),, which would indicate still a third type of compound. The evidence in support of the formulas given above is not conclusive. 1complete investigation was not made, since it
June 15, 1942
ANALYTICAL EDITION
soon became apparent that neither precipitate was well suited for the quantitative estimation of palladium because of solubility. DETERMINATION OF PALLADIUM IN PRESENCE OF XITRATE AKD SULFATE. It was essential to determine whether sulfate and nitrate would interfere in the determination of palladium as the chloride complex. Using the procedure already described and adding varying amounts of sulfate and nitrate, the first ten results given in Table V were obtained. The last six were obtained in a somewhat different manner. Table V shows that even in the presence of large amounts of nitrate and sulfate the procedure gives accurate results, and that even though the nitrate and sulfate complexes are first formed they are rapidly transformed into the chloride compound upon the addition of chloride ion, indicating that the latter is the least soluble.
Summary A method for the gravimetric determination of palladium involves the precipitation of the compound Pd(C4H30CHNOH)&12 with beta-furfuraldoxime. It is shown to give accurate results for amounts of palladium ranging from 2 to 30 mg. By this method palladium may be directly determined in the presence of platinum, ruthenium, rhodium, iridium, iron, cobalt, nickel, copper, manganese, mercury, zinc, aluminum, antimony, bismuth, tin, cadmium, calcium, strontium, barium, magnesium, sodium, potassium, chromium, thorium,
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titanium, zirconium, molybdate, vanadate, tungstate, phosphate, arsenate, borate, selenite, sulfate, and nitrate ions. The determination of palladium in the presence of gold, silver, mercurous, lead, and ceric ions is impossible. The method is believed to have three advantages over the familiar dimethylglyoxime procedure: The precipitate has a higher molecular weight, and hence lower palladium content; as the reagent, beta-furfuraldoxime, is water-soluble, there is no danger of the reagent precipitating out; and furfuraldoxime precipitate is much easier to handle in filtration.
Literature Cited (1) Diehl, H., “Applications of Dioximes t o Analytical Chemistry”, p. 15, G. Frederick Smith Chemical Co., 1940. (2) Feigl, F., Krumholz, P., and Rajmann, E., Mikrochemie, 3, 165 (1931). (3) Hanus, J., Jilek, A., and Lukas, J., Chem. News, 131,401 (1925); 132,l ( 1 9 3 6 ) . (4) Hillebrand, W.F., and Lundell, G. E. F., ”Applied Inorganic Analysis”, p. 636, New York. John Wiley & Sons, 1929. (5) Holser, H., 2. anal. Chem., 95, 392 (1933). (6) Meulen, H. ter. and Hesslinga, J., “Neue Methoden der organisch-chemischen Analyse”, Leipzig, Akademische Verlagsgesellschaft. 1927. (7) Renoll, M. TV., Midgley, T., and Henne, A. L., IND. ENG.CHEM., ANAL.ED.,9, 566 (1937). (8) Schmidt, W., 2. anorg. allgem. Chem., 80,355 (1913). (9) Scott, W. W., “Standard Methods of Chemical Analysis”. 5th ed., p. 266, New York, D. Van Nojtrand Co., 1939 (10) [bid., p. 724. (11) Tschugaeff, L., 2. anorg. Chem., 46, 144 (1905). (12) Yoe, J. H., and Overholser, L. G., J . A m . Chem. Soc., 61,2058 (1939).
Semiautomatic Fractionation A Rapid Analytical Method BASSETT FERGUSON, JR., Ugite Sales Corp., Chester, Penna.
A still head with a constant take-off rate has been developed for a laboratory column. Using the packed column described, an analysis by fractionation may be accomplished in approximately one hour, with sufficient accuracy for most plant control purposes. The analytical still is semiautomatic in operation, one man being able to operate as many as five stills simultaneously.
a
T
H E requirements of analytical methods used in routine control of a continuous chemical process are distinct from those of methods used in research and development work. It is important that any routine analysis selected give necessary and sufficient data for routine plant control. In addition, the test should consume as little time as possible, so that rapid results may be obtained. The simplest technique is usually best for the control laboratory and least likely t o involve serious errors by the operators. I n a petroleum refinery, still performance can usually be determined by simple physical tests on the still products: specific gravity, viscosity, color, and boiling range. These properties sufficiently define the relatively wide-boiling bands of similar hydrocarbons found in a finished petroleum product. In a chemical plant making careful separation of close-boiling
and often homologous hydrocarbons, however, these tests are unsatisfactory for still control. Only occasionally can Satisfactory still performance be defined in terms of product density, refractive index, or by simple chemical test, and the common “boiling range” gives only a vague idea of the percentage composition of a mixture. In the absence of simple analytical controls it is most reasonable to rely on analytical fractionation by distillation, thereby using the same method for analysis that is used for separation in the plant process. But an analytical fractionation is customarily time-consuming and requires more or less constant attention while running. Thus, when routine analysis by distillation was deemed necessary for chemical plant control, it became imperative to develop a method for analytical fractionation sufficiently accurate and rapid for the needs of still control, and requiring a minimum of man power for operation. (By continuous distillation cuts are made which vary in composition from C3 hydrocarbons, through C4 and CSolefins and diolefins, benzene, toluene, and xylene, to aromatic mixtures boiling as high as 300‘ C.) For this purpose the analytical still shown in Figure 1 vas constructed, incorporating the novel features of a constant product take-off rate and automatic temperature recording.
.lipparatus T h e refluxing distillate drains from t h e bulb condenser into cell K , first filling K (capacity 2 t o 3 ml.) and then overflowing
b
